Memory cells and arrays of memory cells

ABSTRACT

A memory cell comprises first, second, third, and fourth transistors individually comprising a transistor gate. First and second ferroelectric capacitors individually have one capacitor electrode elevationally between the transistor gates of the first, second, third, and fourth transistors. Other memory cells are disclosed, as are arrays of memory cells.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 16/050,141, filed Jul. 31, 2018, entitled “MemoryCells and Arrays of Memory Cells”, naming Yasushi Matsubara as inventor,which claimed benefit of U.S. Provisional Patent Application Ser. No.62/548,799, filed Aug. 22, 2017, entitled “Memory Cells and Arrays ofMemory Cells”, naming Yasushi Matsubara as inventor, the disclosures ofwhich are incorporated by reference.

TECHNICAL FIELD

Embodiments disclosed herein pertain to memory cells and to arrays ofmemory cells.

BACKGROUND

Memory is one type of integrated circuitry and is used in computersystems for storing data. Memory may be fabricated in one or more arraysof individual memory cells. Memory cells may be written to, or readfrom, using digit lines (which may also be referred to as bit lines,data lines, or sense lines) and access lines (which may also be referredto as word lines). The digit lines may conductively interconnect memorycells along columns of the array, and the access lines may conductivelyinterconnect memory cells along rows of the array. Each memory cell maybe uniquely addressed through the combination of a digit line and anaccess line.

Memory cells may be volatile, semi-volatile, or non-volatile.Non-volatile memory cells can store data for extended periods of time inthe absence of power. Non-volatile memory is conventionally specified tobe memory having a retention time of at least about 10 years. Volatilememory dissipates and is therefore refreshed/rewritten to maintain datastorage. Volatile memory may have a retention time of milliseconds orless. Regardless, memory cells are configured to retain or store memoryin at least two different selectable states. In a binary system, thestates are considered as either a “0” or a “1”. In other systems, atleast some individual memory cells may be configured to store more thantwo levels or states of information.

A capacitor is one type of electronic component that may be used in amemory cell. A capacitor has two electrical conductors separated byelectrically insulating material. Energy as an electric field may beelectrostatically stored within such material. Depending on compositionof the insulating material, that stored field will be volatile ornon-volatile. For example, a capacitor insulating material includingonly SiO₂ will be volatile. One type of non-volatile capacitor is aferroelectric capacitor which has ferroelectric material as at leastpart of the insulating material. Ferroelectric materials arecharacterized by having two stable polarized states and thereby cancomprise programmable material of a capacitor and/or memory cell. Thepolarization state of the ferroelectric material can be changed byapplication of suitable programming voltages, and remains after removalof the programming voltage (at least for a time). Each polarizationstate has a different charge-stored capacitance from the other, andwhich ideally can be used to write (i.e., store) and to read (i.e.,determine) a memory state without reversing the polarization state untilsuch is desired to be reversed. Less desirable, in some memory havingferroelectric capacitors the act of reading the memory state can reversethe polarization. Accordingly, upon determining the polarization state,a re-write of the memory cell is conducted to put the memory cell intothe pre-read state immediately after its determination. Regardless, amemory cell incorporating a ferroelectric capacitor ideally isnon-volatile due to the bi-stable characteristics of the ferroelectricmaterial that forms a part of the capacitor.

A field effect transistor is another type of electronic component thatmay be used in a memory cell. These transistors comprise a pair ofsource/drain regions having a semiconductive channel regionthere-between. A conductive gate is adjacent the channel region andseparated there-from by a thin gate insulator. Application of a suitablevoltage to the gate allows current to flow from one of the source/drainregions to the other through the channel region. When the voltage isremoved from the gate, current is largely prevented from flowing throughthe channel region. Field effect transistors may also include additionalstructure, for example a reversibly programmable charge-storage regionas part of the gate construction between the gate insulator and theconductive gate. Field effect transistors may be ferroelectric whereinat least some portion of the gate construction (e.g., the gateinsulator) comprises ferroelectric material. The two different polarizedstates of the ferroelectric material in transistors may be characterizedby different threshold voltage (V_(t)) for the transistor or bydifferent channel conductivity for a selected operating voltage.

An individual memory cell may contain one or more transistors and one ormore capacitors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a non-structural diagrammatic schematic of a single 4T-2FCmemory cell in accordance with an embodiment of the invention.

FIG. 2 is a diagrammatic hybrid schematic and structural perspectiveview of a portion of an array of multiple 4T-2FC memory cells of theFIG. 1 schematic in accordance with an embodiment of the invention.

FIG. 3 is a cross-sectional view taken through line 3-3 in FIGS. 4 and5.

FIG. 4 is a cross-sectional view taken through line 4-4 in FIGS. 3 and5.

FIG. 5 is a cross-sectional view taken through line 5-5 in FIGS. 3 and4.

FIG. 6 is a diagrammatic hybrid schematic and structural cross-sectionalview of a portion of another array of multiple 4T-2FC memory cells ofthe FIG. 1 schematic in accordance with an embodiment of the invention,and corresponds to the sectional view as shown in the FIG. 3 structure.

FIG. 7 is a graph of voltage vs. time showing some possible operatingcharacteristics of a 4T-2FC memory cell in accordance with theembodiments of FIGS. 1-6.

FIG. 8 is a non-structural diagrammatic schematic of a single 4T-2FCmemory cell in accordance with an embodiment of the invention.

FIG. 9 is a diagrammatic hybrid schematic and structural perspectiveview of a portion of an array of multiple 4T-2FC memory cells of theFIG. 8 schematic in accordance with an embodiment of the invention.

FIG. 10 is a cross-sectional view taken through line 10-10 in FIGS. 11and 12.

FIG. 11 is a cross-sectional view taken through line 11-11 in FIGS. 10and 12.

FIG. 12 is a cross-sectional view taken through line 12-12 in FIGS. 10and 11.

FIG. 13 is a diagrammatic hybrid schematic and structuralcross-sectional view of a portion of another array of multiple 4T-2FCmemory cells of the FIG. 8 schematic in accordance with an embodiment ofthe invention, and corresponds to the sectional view as shown in theFIG. 10 structure.

FIG. 14 is a graph of voltage vs. time showing some possible operatingcharacteristics of a 4T-2FC memory cell in accordance with theembodiments of FIGS. 8-13.

FIG. 15 is a graph of a hysteresis loop of a ferroelectric capacitor.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the invention comprise single memory cells individuallyhaving four transistors and two ferroelectric capacitors (e.g., in someembodiments as the total number of transistors and capacitors in asingle memory cell regardless of its schematic, and hereafter referredto as a 4T-2FC memory cell) and an array of such memory cells. Firstembodiments thereof are initially described with reference to FIGS. 1-6,with FIG. 1 being a schematic of one single 4T-2FC memory cell MC0 inaccordance with some embodiments.

Referring to FIGS. 2-5, a substrate construction 10 comprises a basesubstrate 11 that may include any one or more ofconductive/conductor/conducting (i.e., electrically herein),semiconductive/semiconductor/semiconducting, orinsulative/insulator/insulating (i.e., electrically herein) materials.Various materials have been formed elevationally over base substrate 11.Materials may be aside, elevationally inward, or elevationally outwardof the FIGS. 2-5-depicted materials. For example, other partially orwholly fabricated components of integrated circuitry may be providedsomewhere above, about, or within base substrate 11. Control and/orother peripheral circuitry for operating components within an array ofmemory cells may also be fabricated, and may or may not be wholly orpartially within a memory array or sub-array. Further, multiple memorysub-arrays may also be fabricated and operated independently, in tandem,or otherwise relative one another. As used in this document, a“sub-array” may also be considered as an array.

Construction 10 comprises an array 13 of 4T-2FC memory cells (e.g., MC0,MC1). Portions of only six (FIG. 5) memory cells MC0 and MC1 arecollectively visible in FIGS. 2-5, with an array likely havingthousands, hundreds of thousands, millions, etc. of memory cells MC* oflike-construction (the symbol “*” being used herein as a genericsubstitute for any specific numbered component). Array 13 comprises rows12 and columns 14 comprising a plurality of ferroelectric capacitors(e.g., FC0T, FC0B, FC1T, FC1B). Pairs of twoimmediately-intra-row-adjacent of the ferroelectric capacitors (e.g., apair FC0T, FC0B and a pair FC1T, FC1B) comprise the two ferroelectriccapacitors of individual 4T-2FC memory cells MC*. The two ferroelectriccapacitors individually comprise a first capacitor electrode (e.g.,CBT0, CBB0, CBT1, CBB1) and a second capacitor electrode (e.g., CP)having a ferroelectric capacitor insulator 16 there-between.Ferroelectric capacitor insulator 16 comprises an annulus 18 radiallyoutward of its first capacitor electrode CBT* or CBB*. Second capacitorelectrode CP comprises a portion 20 (FIG. 5) radially outward offerroelectric capacitor insulator annulus 18. Further, second capacitorelectrode CP is the second capacitor electrode of, and is common to, allof the plurality of ferroelectric capacitors FC*T, FC*B in this exampleembodiment.

Columns 14 comprise pairs (e.g., a pair DLT0, DLB0 and a pair DLT1,DLB1) of first comparative digit lines (e.g., DLT0, DLT1) and secondcomparative digit lines (e.g., DLB0, DLB1) that areimmediately-inter-column-adjacent one another. Such pairs mayindividually connect to a read/sense amplifier SA (FIG. 1, theconstruction of which may be at an edge of array 13), which may serve toamplify a difference signal that arises on the digit line pair when amemory cell MC* is read-accessed.

Rows 12 and columns 14 comprise shorting transistors (e.g., MCBRT0,MCBRB0, MCBRT1, MCBRB2) individually comprising a transistor gate 28(FIG. 4) that comprises a portion of an individual shorting control line(e.g., CBR0, CBR1, CBR2) that interconnects multiple of the shortingtransistors along individual rows 12. Pairs (e.g., a pair MCBRT0, MCBRB0and a pair MCBRT1, MCBRB1) of two immediately-intra-row-adjacentshorting transistors comprise a first two transistors of individual4T-2FC memory cells MC*. Such first two shorting transistors inindividual 4T-2FC memory cells MC* individually are directlyelectrically coupled to and between different ones of respective firstcapacitor electrodes CBT*, CBB* and common second capacitor electrodeCP.

Rows 12 and columns 14 comprise selecting transistors (e.g., MWL0T,MWL0B, MWL1T, MWL1B, and which alternately may be considered as accesstransistors) individually comprising a transistor gate 40 (FIG. 4) thatcomprises a portion of an individual word line (e.g., WL0, WL1, WL2)that interconnects multiple of the selecting transistors alongindividual rows 12. Pairs (e.g., a pair MWL0T, MWL0B and a pair MWL1T,MWL1B) of two immediately-intra-row-adjacent of the selectingtransistors comprise a second two transistors of individual 4T-2FCmemory cells MC*. Such second two selecting transistors in individual4T-2FC memory cells MC* individually are directly electrically coupledto and between different ones of respective first capacitor electrodesCBT*, CBB* and different ones of first comparative digit lines DLT* orsecond comparative digit lines DLB* of individual pairs (e.g.,DLT0/DLB0, DLT1/DLB1) of first and second comparative digit lines.

One of (a) the word lines, or (b) the shorting control lines is aboveall of the plurality of the ferroelectric capacitors, and the other of(a) or (b) is below all of the plurality of ferroelectric capacitors.FIGS. 2-5 depict an embodiment wherein (b): the shorting control linesare above all of the plurality of the ferroelectric capacitors. Analternate embodiment construction 10 a of an array 13 a is shown in FIG.6 (analogous to FIG. 3) wherein (a): the word lines are above all of theplurality of the ferroelectric capacitors. Like numerals from theabove-described embodiments have been used where appropriate, with someconstruction differences being indicated with the suffix “a”. Any otherattribute(s) or aspect(s) as shown and/or described herein with respectto other embodiments may be used in the FIG. 6 embodiment.

In one embodiment, all of the first and second comparative digit linesare either above or below all of the ferroelectric capacitors with theword lines. In other words, in such embodiment, all of the first andsecond comparative digit lines are either above or below all of theferroelectric capacitors on whichever up-side or down-side the wordlines are on, and as is shown by way of example only with respect toeach of the FIGS. 2-5 embodiment and the FIG. 6 embodiment. In one suchembodiment, the word lines are below all of the ferroelectric capacitorsand all of the first and second comparative digit lines are below all ofthe word lines (e.g., the FIGS. 2-5 embodiment). In an alternate suchembodiment, the word lines are above all of the ferroelectric capacitorsand all of the first and second comparative digit lines are above all ofthe word lines (e.g., the FIG. 6 embodiment).

In one embodiment and as shown, the shorting transistors and theselecting transistors are elevationally-extending transistors, and inone such embodiment are vertical or within 10° of vertical. In oneembodiment, 4T-2FC memory cells MC* individually comprise a firstelevationally-extending pillar (e.g., 24) and a secondelevationally-extending pillar (e.g, 26) that are intra-row-spacedrelative one another. In such embodiment, the shorting transistors andthe selecting transistors of individual 4T-2FC memory cells MC* may beconsidered as individually comprising source/drain regions and anelevationally-extending channel region there-between. For example, FIGS.3 and 4 show shorting transistors MCBRT*, MCBRB* individually comprisinga source/drain region 35, a source/drain region CBT0, CBB0, CBT1, CBB1,and an elevationally-extending channel region 32 there-between.Source/drain regions 35 and second capacitor electrode CP may beconsidered as a single or collective electrode, and with the depictedtwo elevationally-spaced CP portions thereof being directly electricallycoupled with one another in the FIGS. 2-6 embodiments (e.g. by aschematic interconnect line 25 the construction of which may be at anedge of array 13). Further, for example, selecting transistors MWL*T,MWL*B of individual 4T-2FC memory cells MC* individually comprise asource/drain region 37, a source/drain region CBT0, CBB0, CBT1, CBB1,and an elevationally-extending channel region 33 there-between. Channelregions 32 of shorting transistors MCBRT, MCBRB are intra-row-spacedfrom one another at one level 36 and channel regions 33 of selectingtransistors MWL*T, MWL*B are intra-row-spaced from one another atanother level 34 that is elevationally-spaced from level 36.

First pillars 24 individually comprise channel regions 32, 33 of one ofshorting transistors MCBRT*, MCBRB* and one of selecting transistorsMWL*T, MWL*B, respectively, of individual 4T-2FC memory cells MC*. Firstpillars 24 also individually comprise the source/drain regions of therespective ones of the shorting transistors and the respective ones ofthe selecting transistors of individual 4T-2FC memory cells MC*. Firstpillars 24 additionally individually comprise the first capacitorelectrode CBBT*, CBBB* of one of the two ferroelectric capacitors ofindividual 4T-2FC memory cells MC*. Second pillars 26 individuallycomprise channel regions 32, 33 of the other of the shorting transistorsand the other of the selecting transistors, respectively, of individual4T-2FC memory cells MC*. Second pillars 26 also individually comprisethe source/drain regions of the respective others of the shortingtransistors and the respective others of the selecting transistors ofindividual 4T-2FC memory cells MC*. Second pillars 26 additionallyindividually comprise the first capacitor electrode of the other of thetwo ferroelectric capacitors of individual 4T-2FC memory cells MC*.

Any other attribute(s) or aspect(s) as shown and/or described hereinwith respect to other embodiments may be used in the FIGS. 1-5embodiment.

An alternate example embodiment construction 10 b of an array 13 b of4T-2FC memory cells MC* is next described with reference to FIGS. 8-12.Like numerals from the above-described embodiments have been used whereappropriate, with some construction differences being indicated with thesuffix “b” or with different numerals. Construction 10 b differs in partfrom construction 10 in that the second capacitor electrode of theferroelectric capacitors is not common to all of the plurality of theferroelectric capacitors. Rather, array 13 b has second capacitorelectrodes (e.g., CP1, CP2) of the two ferroelectric capacitors (e.g.,FC*T, FC*B) of individual 4T-2FC memory cells MC* electrically isolatedfrom one another (i.e., CP1 and CP2 are not directly electricallycoupled to one another). First capacitor electrodes CBT*, CBB* of thetwo ferroelectric capacitors of individual 4T-2FC memory cells MC* arealso electrically isolated from one another, and for example as is shownin the first-described embodiments. The depicted twoelevationally-spaced CP1 portions are directly electrically coupled withone another as are the depicted two elevationally-spaced CP1 portions(e.g. by a schematic interconnect line 25 for the CP1 portions and by aschematic interconnect line 27 for the CP2 portions, and theconstructions of which may be at an edge of array 13 b).

Additionally, in construction 10 b, columns 14 comprise pairs (e.g., apair DLT0, DLT1) of immediately-inter-column-adjacent first comparativedigit lines (DLT0, DLT1) and pairs (e.g., a pair DLB0, DLB1) ofimmediately-inter-column-adjacent second comparative digit lines (DLB0,DLB1). Individual memory cells MC* comprise one of first comparativedigit lines DLT0 or DLT1 and one of second comparative digit lines DLB0or DLB1. Accordingly, all of the components of an individual memory cellMC* are not all immediately-intra-row-adjacent one another as, forexample, is shown in constructions 10/10 a of the first-describedembodiments.

Rows 12 and columns 14 again comprise shorting transistors MCBRT*,MCBRB* individually comprising a transistor gate 28 that comprises aportion of an individual shorting control line CBR* that interconnectsmultiple of the shorting transistors along individual rows 12. However,pairs (e.g., a pair MCBRT0, MCBRB0 and a pair MCBRT1, MCBRB1) ofevery-other-ones of the shorting transistors in individual rows 12comprise a first two transistors of individual 4T-2FC memory cells MC*.The first two shorting transistors in individual 4T-2FC memory cells MC*individually are directly electrically coupled to and between differentones of the respective first capacitor electrodes CBT*, CBB* anddifferent ones of the respective second capacitor electrodes CP*, CP*.

Rows 12 and columns 14 again comprise selecting transistors MWL*T, MWL*Bindividually comprising a transistor gate 40 that comprises a portion ofan individual word line WL* that interconnects multiple of the selectingtransistors along individual rows 12. However, pairs (e.g., a pairMWL0T, MWL0B and a pair MWL1T, MWL1B) of every-other-ones of theselecting transistors in individual rows 12 comprise a second twoselecting transistors of individual 4T-2FC memory cells MC*. The secondtwo selecting transistors in individual 4T-2FC memory cells MC*individually are directly electrically coupled to and between differentones of the respective first capacitor electrodes CBT*, CBB* anddifferent ones of the respective first or second comparative digit linesDLT*, DLB*. One of (a) the word lines or (b) the shorting control linesis above all of the ferroelectric capacitors, and the other of (a) or(b) is below all of the ferroelectric capacitors. FIGS. 9-12 show anexample embodiment wherein (b): the shorting control lines are above allof the ferroelectric capacitors. FIG. 13 shows an alternate exampleembodiment wherein (a): the word lines are above all of theferroelectric capacitors. Like numerals from the above-describedembodiments have been used where appropriate, with some constructiondifferences being indicated with the suffix “c”. Any other attribute(s)or aspect(s) as shown and/or described herein may be used with respectto the embodiment of FIGS. 8-12 and the embodiment of FIG. 13.

Some embodiments of the invention comprise a 4T-2FC memory cellregardless of whether being of the FIG. 1 schematic, the FIG. 8schematic, or some other schematic, and may include an array of such4T-2FC memory cells. In one such embodiment, a 4T-2FC memory cellcomprises first, second, third, and fourth transistors (e.g., MCBRT0,MCBRB0, MWL0T, MWL0B, respectively). The 4T-2FC memory cell comprisesfirst and second ferroelectric capacitors (e.g., FC0T, FC0B,respectively) individually having one capacitor electrode (e.g., CP inthe FIG. 1 schematic, CP* in the FIG. 8 schematic) at twoelevationally-spaced levels (e.g., a level 44, a level 46). Aferroelectric capacitor insulator (e.g., 16) is between the onecapacitor electrode and another capacitor electrode (e.g., CBT*, CBB*)in one of the two levels (e.g., 44 in construction 10) and noferroelectric capacitor insulator is between the one and the anothercapacitor electrodes in the other of the two levels (e.g., 46 inconstruction 10 at least because neither of CBT* and CBB* is anywherewithin level 46).

In one embodiment, the first, second, third, and fourth transistorsindividually comprise a transistor gate (e.g., 28, 40), with one of thegates (e.g., 28 in construction 10) being elevationally between the twoelevationally-spaced levels. In one such embodiment, another one of thegates (e.g., 40 in construction 10) is not elevationally between the twoelevationally-spaced levels. In one embodiment, multiple of thetransistor gates (e.g., 28 in construction 10) are elevationally betweenthe two elevationally-spaced levels. In one such embodiment, two andonly two of the transistor gates are elevationally between the twoelevationally-spaced levels. In one embodiment, two of the first,second, third, and fourth transistors are shorting transistors (e.g.,MCBR0T, MCBR0B) that are directly electrically coupled to and betweendifferent ones of the respective one capacitor electrode and differentones of the another capacitor electrodes.

In one embodiment, an array (e.g., 13, 13 a) comprises the 4T-2FC memorycell as one memory cell of a plurality of 4T-2FC memory cells oflike-construction relative one another, and wherein the one capacitorelectrode is the one capacitor electrode of, and that is common to, allof the ferroelectric capacitors of the plurality of the 4T-2FC memorycells. In another embodiment, an array (e.g., 13 b, 13 c) comprises the4T-2FC memory cell as one memory cell of a plurality of 4T-2FC memorycells of like-construction relative one another. In such embodiment, theone capacitor electrodes of the first and second ferroelectriccapacitors in individual of the 4T-2FC memory cells are electricallyisolated from one another. In such embodiment, the another capacitorelectrodes of the first and second ferroelectric capacitors in theindividual 4T-2FC memory cells are electrically isolated from oneanother.

Any other attribute(s) or aspect(s) as shown and/or described herein maybe used.

Additional embodiments of the invention comprise a 4T-2FC memory cellregardless of whether being of the FIG. 1 schematic, the FIG. 8schematic, or some other schematic, and may include an array of such4T-2FC memory cells. In one such embodiment, a 4T-2FC memory cellcomprises first, second, third, and fourth transistors (e.g., MCBRT0,MCBRB0, MWL0T, MWL0B, respectively) individually comprising a transistorgate (e.g., 28, 40). The 4T-2FC memory cell comprises first and secondferroelectric capacitors (e.g., FC0T, FC0B, respectively) individuallyhave one capacitor electrode (e.g., CBT0, CBB0) elevationally betweenthe transistor gates of the first, second, third, and fourthtransistors. In one embodiment, the first and second ferroelectriccapacitors individually have another capacitor electrode (e.g., CP, CP1,CP2) some portion of which (e.g., that within level 44 in construction10) is elevationally between the transistor gates of the first, second,third, and fourth transistors. In one embodiment, the first and secondferroelectric capacitors individually have another capacitor electrode(e.g., CP, CP1, CP2) only a portion of which (e.g., that within level 44in construction 10) is elevationally between the transistor gates of thefirst, second, third, and fourth transistors. In one embodiment, anarray (e.g., 13, 13 a, 13 b, 13 c) comprises the 4T-2FC memory cell asone memory cell of a plurality of 4T-2FC memory cells oflike-construction relative one another. Any other attribute(s) oraspect(s) as shown and/or described herein may be used.

Additional embodiments of the invention comprise a 4T-2FC memory cellregardless of whether being of the FIG. 1 schematic, the FIG. 8schematic, or some other schematic, and may include an array of such4T-2FC memory cells. In one such embodiment, a 4T-2FC memory cellcomprises first, second, third, and fourth transistors (e.g., MCBRT0,MCBRB0, MWL0T, MWL0B, respectively). The 4T-2FC memory cell comprisesfirst and second ferroelectric capacitors (e.g., FC0T, FC0B,respectively) individually comprising first and second capacitorelectrodes (e.g., CBT0, CBB0, and CP, CP1, CP2, respectively) having aferroelectric capacitor insulator (e.g., 16) there-between. The firstcapacitor electrode comprises an elevationally-extending pillar (e.g.,24, 26). The ferroelectric capacitor insulator comprises an annulus(e.g., 18) radially outward of the first capacitor electrode. The secondcapacitor electrode comprises a portion (e.g., 20) radially outward ofthe ferroelectric-capacitor-insulator annulus. In one embodiment,conductive material of the pillar (e.g., material of CBT*, CBB*) extendsentirely diametrically across all of the pillar.

In one embodiment, the first, second, third, and fourth transistorsindividually comprise a transistor gate (e.g., 28, 40). The gates (e.g.,28 in construction 10) of two of the first, second, third, and fourthtransistors (e.g., MCBRT0, MCBRB0 in construction 10) are above theportion of the second capacitor electrode that is radially outward ofthe ferroelectric-capacitor-insulator annulus. The gates (e.g., 40 inconstruction 10) of another two of the first, second, third, and fourthtransistors (e.g., MWL0T, MWL0B in construction 10) are below theportion of the second capacitor electrode that is radially outward ofthe ferroelectric-capacitor-insulator annulus.

Any other attribute(s) or aspect(s) as shown and/or described herein maybe used.

Additional embodiments of the invention comprise a 4T-2FC memory cellregardless of whether being of the FIG. 1 schematic, the FIG. 8schematic, or some other schematic, and may include an array of such4T-2FC memory cells. In one such embodiment, a 4T-2FC memory cellcomprises first and second laterally-spaced and elevationally-extendingpillars (e.g., 24, 26, respectively). The 4T-2FC memory cell comprisesfirst and second ferroelectric capacitors (e.g., FC0T, FC0B,respectively) individually comprising first and second capacitorelectrodes (e.g., CBT0, CBB0, and CP, CP1, CP2, respectively) having aferroelectric capacitor insulator (e.g., 16) there-between. The 4T-2FCmemory cell comprises first, second, third, and fourthelevationally-extending transistors (e.g., MCBRT0, MCBRB0, MWL0T, MWL0B,respectively) individually comprising source/drain regions (e.g., 35,CBT0, CBB0, 37), an elevationally-extending channel region (e.g., 32,33) between the source/drain regions and a transistor gate (e.g., 28,40) operatively proximate the channel region (e.g., a gate insulator 17being between the channel and the gate). The channel regions (e.g., 32in construction 10) of the first and second transistors (e.g., MCBRT0,MCBRB0 in construction 10) are laterally adjacent one another above thesecond capacitor electrodes. The channel regions (e.g., 33 inconstruction 10) of the third and fourth transistors (e.g., MWL0T, MWL0Bin construction 10) are laterally adjacent one another below the secondcapacitor electrodes. The first pillar comprises the source/drainregions and the channel regions of the first and third transistors. Thefirst pillar comprises the first capacitor electrode of the firstferroelectric capacitor. The second pillar comprises the source/drainregions and the channel regions of the second and fourth transistors.The second pillar comprises the first capacitor electrode of the secondferroelectric capacitor. Any other attribute(s) or aspect(s) as shownand/or described herein may be used.

In some embodiments, any one or more of the elevationally-extendingfeatures is formed to be vertical or within 10° of vertical.

FIG. 7 is a graph of voltage vs. time showing some possible operatingcharacteristics of a 4T-2FC memory cell in accordance with theembodiments of FIGS. 1-6. More specifically, FIG. 7 is the timingdiagram of a read and write cycle for a FIGS. 1-6 memory cell MC0. Sinceno voltage difference may be allowed across ferroelectric capacitorsFC0T and FC0B, the equilibrium signal CBR0 is at VCCP during stand-by.At the beginning of a cycle, the equilibrium CBR0 is turned off todisconnect cell plate CP from the other node of ferroelectric capacitorFC0T, CBT0 which is at the same potential as cell plate CP. Digit linesDLT0 and DLB0 are pre-charged to ground during stand-by. As soon as CBR0is turned off, the digit lines are disconnected from ground and becomevoltage-floating and cell plate CP is raised to VMSA while CBT0 and CBB0are both pulled up to a level similar to that of cell plate CP due tocapacitance of the ferroelectric capacitor which is sufficiently largerthan the parasitic capacitance value of CBT0 or CBB0. Then, to accessferroelectric capacitors FC0T and FC0B, word line WL0 is raised up toVCCP level. As soon as WL0 reaches the threshold voltage of selectingtransistors MWL0T and MWL0B, a charge transfer occurs between digitlines DLT0, DLB0 and ferroelectric capacitor FC0T, FC0B, respectively.The digit line voltages are established according to their relativecapacitances. The ferroelectric capacitor's two capacitances, a 0 or a1, can be approximated by one of two linear capacitors C0 or C1 as shownin FIG. 15. Thus the voltage developed on digit lines DLT0 and DLB0 canbe one of two values, V0 or V1:V _(digit line) =V0={C0/(C0+C _(digit line))}×VMSA (if cell data is a 0)V _(digit line) =V1={C1/(C1+C _(digit line))}×VMSA (if cell data is a 1)The data on capacitors FC0T and FC0B is complimentary to each other.Therefore, if FC0T is a 1, then FC0B is a 0, and vice versa. As soon asthe developed voltage difference between DLT0 and DLB0 is stable,read/sense amplifier SA drives them to full scale voltages VMSA andground level and the read data will finally be written back to thecapacitors as follows: when cell plate CP is high, DLT0 is clamped toground level and cell plate CP is VMSA, then data of a 0 is written tocapacitor FC0T. On the other hand, when cell plate CP is at ground anddigit line DLB0 is at VMSA, compliment data of a 1 is written tocapacitor FC0B. After data is written back to the capacitors, digitlines and cell plates CP are driven to ground and the equilibrium signalCBR0 turns on to ensure no voltage difference across the top and bottomnodes of ferroelectric capacitors FC0T and FC0B which may be needed toavoid the capacitor from losing signal in the capacitors due to imprintor disturb or retention issues. At the end of the cycle, word line WL0is turned off to ground level.

FIG. 14 is a graph of voltage vs. time showing some possible operatingcharacteristics of a 4T-2FC memory cell MC0 in accordance with theembodiments of FIGS. 8-13. The top graph of FIG. 14 represents thepotential curve of the electrode of capacitor FC0B which is connected totransistor MWL0B. The middle graph of FIG. 14 represents the potentialcurve of the electrode of capacitor FC0T which is connected totransistor MWL0T. The bottom graph of FIG. 14 represents the potentialcurve of word line WL0 and of the two successive read-accesses areshown, whereby a logic “0” is stored in capacitors FC0T, FC0B. Beforethe memory cells are read-accessed, the two digit lines DLT0, DLB0 arepre-charged to a common bias potential VMSA=1.6V. This corresponds tothe average value of the two plate potentials CP1=0V and about CP=3.2V.Word line WL0 then becomes active with a positive edge. TransistorsMWL0T, MWL0B are thereby switched “on”/to conduct, so that a chargeequalization occurs between digit lines DLT0, DLB0 and capacitors FC0T,FC0B. In the case of a stored logic “0”, the potential of digit lineDLT0 is slightly reduced, and the potential of digit line DLB0 isslightly increased. Next, read/sense amplifier SA is activated, wherebythe difference signal on digit line pair DLT0, DLB0 is amplified. Theread-access ends with a negative edge of potential on word line WL0.

In this document unless otherwise indicated, “elevational”, “higher”,“upper”, “lower”, “top”, “atop”, “bottom”, “above”, “below”, “under”,“beneath”, “up”, and “down” are generally with reference to the verticaldirection. “Horizontal” refers to a general direction (i.e., within 10degrees) along a primary substrate surface and may be relative to whichthe substrate is processed during fabrication, and vertical is adirection generally orthogonal thereto. Reference to “exactlyhorizontal” is the direction along the primary substrate surface (i.e.,no degrees there-from) and may be relative to which the substrate isprocessed during fabrication. Further, “vertical” and “horizontal” asused herein are generally perpendicular directions relative one anotherand independent of orientation of the substrate in three-dimensionalspace. Additionally, “elevationally-extending” and “extendingelevationally” refer to a direction that is angled away by at least 450from exactly horizontal. Further, “extend(ing) elevationally” and“elevationally-extending” with respect to a field effect transistor arewith reference to orientation of the transistor's channel length alongwhich current flows in operation between the source/drain regions. Forbipolar junction transistors, “extend(ing) elevationally” and“elevationally-extending” are with reference to orientation of the baselength along which current flows in operation between the emitter andcollector.

Further, “directly above”, “directly under”, and “directly below”require at least some lateral overlap (i.e., horizontally) of two statedregions/materials/components relative one another. Also, use of “above”not preceded by “directly” only requires that some portion of the statedregion/material/component that is above the other be elevationallyoutward of the other (i.e., independent of whether there is any lateraloverlap of the two stated regions/materials/components). Analogously,use of “under” or “below” not preceded by “directly” only requires thatsome portion of the stated region/material/component that is under/belowthe other be elevationally inward of the other (i.e., independent ofwhether there is any lateral overlap of the two statedregions/materials/components).

Any of the materials, regions, and structures described herein may behomogenous or non-homogenous, and regardless may be continuous ordiscontinuous over any material which such overlie. Further, unlessotherwise stated, each material may be formed using any suitable oryet-to-be-developed technique, with atomic layer deposition, chemicalvapor deposition, physical vapor deposition, epitaxial growth, diffusiondoping, and ion implanting being examples.

Additionally, “thickness” by itself (no preceding directional adjective)is defined as the mean straight-line distance through a given materialor region perpendicularly from a closest surface of animmediately-adjacent material of different composition or of animmediately-adjacent region. Additionally, the various materials orregions described herein may be of substantially constant thickness orof variable thicknesses. If of variable thickness, thickness refers toaverage thickness unless otherwise indicated, and such material orregion will have some minimum thickness and some maximum thickness dueto the thickness being variable. As used herein, “different composition”only requires those portions of two stated materials or regions that maybe directly against one another to be chemically and/or physicallydifferent, for example if such materials or regions are not homogenous.If the two stated materials or regions are not directly against oneanother, “different composition” only requires that those portions ofthe two stated materials or regions that are closest to one another bechemically and/or physically different if such materials or regions arenot homogenous. In this document, a material, region, or structure is“directly against” another when there is at least some physical touchingcontact of the stated materials, regions, or structures relative oneanother. In contrast, “over”, “on”, “adjacent”, “along”, and “against”not preceded by “directly” encompass “directly against” as well asconstruction where intervening material(s), region(s), or structure(s)result(s) in no physical touching contact of the stated materials,regions, or structures relative one another.

Herein, regions-materials-components are “electrically coupled” relativeone another if in normal operation electric current is capable ofcontinuously flowing from one to the other, and does so predominately bymovement of subatomic positive and/or negative charges when such aresufficiently generated. Another electronic component may be between andelectrically coupled to the regions-materials-components. In contrast,when regions-materials-components are referred to as being “directlyelectrically coupled”, no intervening electronic component (e.g., nodiode, transistor, resistor, transducer, switch, fuse, etc.) is betweenthe directly electrically coupled regions-materials-components.

Additionally, “metal material” is any one or combination of an elementalmetal, a mixture or an alloy of two or more elemental metals, and anyconductive metal compound.

Use of “row” and “column” in this document is for convenience indistinguishing one series or orientation of features from another seriesor orientation of features and along which components have been or willbe formed. “Row” and “column” are used synonymously with respect to anyseries of regions, components, and/or features independent of function.Regardless, the rows may be straight and/or curved and/or paralleland/or not parallel relative one another, as may be the columns.Further, the rows and columns may intersect relative one another at 90°or at one or more other angles.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

The invention claimed is:
 1. A memory cell comprising: first, second,third, and fourth transistors; and first and second ferroelectriccapacitors individually having one capacitor electrode at twoelevationally-spaced levels, a ferroelectric capacitor insulator beingbetween the one capacitor electrode and another capacitor electrode inone of the two elevationally-spaced levels and no ferroelectriccapacitor insulator being between the one and the another capacitorelectrodes in the other of the two elevationally-spaced levels.
 2. Thememory cell of claim 1 wherein the first, second, third, and fourthtransistors individually comprise a transistor gate, one of the gatesbeing elevationally between the two elevationally-spaced levels.
 3. Thememory cell of claim 2 wherein another one of the gates is notelevationally between the two elevationally-spaced levels.
 4. The memorycell of claim 2 wherein multiple of the transistor gates areelevationally between the two elevationally-spaced levels.
 5. The memorycell of claim 4 wherein two and only two of the transistor gates areelevationally between the two elevationally-spaced levels.
 6. The memorycell of claim 1 wherein two of the first, second, third, and fourthtransistors are shorting transistors that are directly electricallycoupled to and between different ones of the respective one capacitorelectrode and different ones of the respective another capacitorelectrodes.
 7. An array comprising the memory cell of claim 1 as onememory cell of a plurality of memory cells of like-construction relativeone another, wherein the one capacitor electrode is the one capacitorelectrode of, and that is common to, all of the ferroelectric capacitorsof the plurality of the memory cells.
 8. An array comprising the memorycell of claim 1 as one memory cell of a plurality of memory cells oflike-construction relative one another, wherein, the one capacitorelectrodes of the first and second ferroelectric capacitors inindividual of the memory cells are electrically isolated from oneanother; and the another capacitor electrodes of the first and secondferroelectric capacitors in the individual memory cells are electricallyisolated from one another.
 9. The memory cell of claim 1 wherein thefirst, second, third, and fourth transistors individually areelevationally-extending to be vertical or within 10° of vertical. 10.The memory cell of claim 1 wherein the memory cell is 4T-2FC.